This invention relates to pneumatic conveyance devices. Typical pneumatic conveyance devices use a high vacuum suction device which relies upon large quantities of air or other fluids to achieve material movement into and through a nozzle. For instance, there are a variety of venturi-type nozzles which use an air supply flow that is substantially parallel to the introduced material flow. As a general rule, the more shallow, i.e., close to 0°, of the air supply introduction angle, the greater the amount of suction which may be achieved, provided a greater volume of air is supplied. Such devices are known in the art including the devices set forth in U.S. Pat. No. 3,512,841 and U.S. Pat. No. 5,071,289, both of which are incorporated herein by reference. The patents referenced above use a high air flow with an entry angle of the air to the nozzle of close to a 0° angle. As used herein, the angle referred to is in reference to the central conveyance axis of the device. While such devices are useful for creating a high suction, there are inherent limitations in their design and operation both as to the particle size, conveyance height, and overall efficiency for removal of a solid material.
Conventional pneumatic conveyors are limited in their capacity and the type of materials to be handled. While conventional pneumatic conveyors are useful for certain materials such as powders, granules, or pellets, there is a need for a pneumatic conveyor which can handle more diverse materials in terms of size, shape, and composition as well as a nozzle capable of removing materials from depths which cannot be achieved using a traditional vacuum-type nozzle.
A vacuum-type nozzle such as the ones described above are theoretically incapable of removing solid debris, liquids, or combinations of mixed liquid and solid waste from depths greater than approximately 32 feet. 32 feet is the maximum theoretical conveyance height that can be generated by a vacuum at sea level. However, given the inefficiencies of a vacuum and friction within a conveyance tube, depths greater than approximately 25 feet cannot be reliably serviced by a vacuum-type nozzle. Further, the efficiency of a vacuum-type nozzle does not provide an adequate mechanism for conveying materials great distances through a pneumatic hose or similar structure. There are a number of situations such as deep waste tanks and similar environments which accumulate waste material and debris which must be removed. Many of these environments have a depth below grade level in excess of 40 feet and, therefore, a pneumatic suction apparatus is impossible to use. Similarly, there are many situations where materials need to be conveyed a distance of 70 to 100 feet or more through a substantially horizontal conveyance hose. The vacuum-type nozzles described above lack sufficient air movement properties to achieve transport of materials such distances.
The ability to achieve an efficient material conveyance through a pneumatic nozzle and hose is directly correlated with the efficiency of the material conveyance apparatus. Material conveyance using air is a turbulent flow and associated with known pressure drop values as turbulent air passes through a hose or similar structure. It is known that the pressure drop of turbulent air through a conduit is an exponential function of the inside diameter of the conduit. Accordingly, any increase in the efficiency of the nozzle and nozzle delivery process can achieve a large effect on the transport efficiency.
Accordingly, there remains room for improvement and variation within the art directed to an apparatus and techniques for removing materials which overcome the inherent limitations of a venturi-type suction nozzle.